The invention relates to an impact beam for a vehicle body which has an oblong, box-type hollow profile.
An impact beam of the generic type is disclosed in EP 0 467 829 B1. The impact beam there is extruded and is designed as a box-type, elongate hollow profile. In this case, the hollow profile has an inner profile wall, which faces the vehicle interior and serves as an inner chord, and an opposite, outer profile wall, which serves as an outer chord. The two profile walls are connected to each other by transverse walls which have a comparatively small wall thickness in comparison with the profile walls. In order to obtain a uniform deformation of the beam during the impact and at the same time to counteract the collapse of the compression chord of the beam, the outer chord, holes which lie outside the center of gravity of the beam are to be provided in the outer chord. In spite of this measure, there is not sufficient security against a collapse during an impact. If, in addition, the lightweight construction aspect is important, the strength and rigidity of the beam are not very high if the beam consists of light metal.
The invention is based on the object of developing an impact beam of the generic type to the effect that the latter, despite a lightweight manner of construction, provides sufficient rigidity and strength in the event of an impact together with an increased absorption of energy.
The object is achieved according to the invention by an impact beam for a vehicle body with an oblong, box-type hollow profile, and an oblong, planar, fiber-reinforced plastic part fitted at least on the rear side of the hollow profile facing the vehicle interior.
The interaction of the hollow profile with a planar, fiber-reinforced plastic part concentrates the properties which are favorable in each case in respect of lightweight construction, rigidity and strength of the impact beam. The circumferentially closed nature of the hollow profile provides a high resistance for the beam against shearing forces while the fiber-reinforced plastic part counteracts the bending moment, which arises in the beam during an impact load, by means of the tension of its fibers which run parallel to the beam, and therefore contributes a high degree of elastic rigidity and strength in relation to bending and forces acting in the axial direction. In this case, the absorption of energy and the rupture-free deformation distance which can be obtained are particularly high. Owing to the planar box-type shape, a particular good attachment of the plastic part to the hollow profile is provided. The outlay for production of the beam according to the invention is low because of the ease with which the plastic part can be fitted and produced and the ease of which the hollow profile can be fitted. The invention also enables the formation of a beam which is substantially narrower and/or has a smaller wall thickness than conventional beams while the rigidity and strength remain the same. This enables more slender structures to be realized at a suitable location on the vehicle body without having to accept losses in rigidity and strength. In addition, the weight of the beam and therefore of the entire body is reduced. The beam can be used on the vehicle wherever only small curvatures occur and where loads act toward the vehicle. In this case, the beam can be used as a bending support for the bumper or as a part thereof, in the central part of the lateral roof frame or else as side impact protection. The use of a roof bow for connecting the B-pillars is likewise conceivable.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.